<p class="shortdesc">本文主要介绍可以通过RDS管理控制台修改的主要参数。</p> <section class="section" id="Supported_Parameters__section_ph4_pyz_jsb"><h2 class="doc-tairway">背景信息</h2> <p class="p">RDS-MySQL服务提供了参数管理功能，您可以根据业务需求，设置MySQL引擎相关的高级参数，进行性能调优。</p> </section> <section class="section" id="Supported_Parameters__section_jgx_4yz_jsb"><h2 class="doc-tairway">参数说明</h2> <table class="table" id="Supported_Parameters__table_khs_1q5_n5b"><caption></caption><colgroup><col><col><col><col></colgroup><thead class="thead"> <tr class="row"> <th class="entry" id="Supported_Parameters__table_khs_1q5_n5b__entry__1"> <p class="p">参数</p> </th> <th class="entry" id="Supported_Parameters__table_khs_1q5_n5b__entry__2"> <p class="p">默认值</p> </th> <th class="entry" id="Supported_Parameters__table_khs_1q5_n5b__entry__3"> <p class="p">是否需要重启实例</p> </th> <th class="entry" id="Supported_Parameters__table_khs_1q5_n5b__entry__4"> <p class="p">说明</p> </th> </tr> </thead><tbody class="tbody"> <tr class="row"> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__1 "> <p class="p">back_log</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__2 "> <p class="p">3000</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__3 "> <p class="p">是</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__4 "> <p class="p">MySQL每处理一个连接请求时都会创建一个新线程与之对应。在主线程创建新线程期间，如果前端应用有大量的短连接请求到达数据库，如果等待的连接数量超过back_log的值，则MySQL将不会接受新的连接请求。如果需要MySQL能够处理大量的短连接，需要提高此参数的大小。</p> </td> </tr> <tr class="row"> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__1 "> <p class="p">innodb_autoinc_lock_mode</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__2 "> <p class="p">1</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__3 "> <p class="p">是</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__4 "> <p class="p">自增主键的锁机制：</p> <ul class="ul" id="Supported_Parameters__ul_lhs_1q5_n5b"> <li class="li">0：传统模式</li> <li class="li">1：递增模式</li> <li class="li">2：无锁定</li> </ul> <p class="p">RDS-MySQL默认取值为1，表示InnoDB使用轻量级别的mutex锁来获取自增锁，替代最原始的表级锁。</p> </td> </tr> <tr class="row"> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__1 "> <p class="p">query_cache_size</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__2 "> <p class="p">3145728</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__3 "> <p class="p">否</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__4 "> <p class="p">查询缓冲区的最大长度。</p> <p class="p">默认情况下，不开启，最大缓冲区最大长度为0。</p> <p class="p">取值需为1024的倍数，否则会向下取最接近的数值。</p> </td> </tr> <tr class="row"> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__1 "> <p class="p">net_write_timeout</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__2 "> <p class="p">60</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__3 "> <p class="p">否</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__4 "> <p class="p">等待将一个block发送给客户端的超时时间。</p> </td> </tr> <tr class="row"> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__1 "> <p class="p">tmp_table_size</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__2 "> <p class="p">33554432</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__3 "> <p class="p">否</p> </td> <td class="entry" headers="Supported_Parameters__table_khs_1q5_n5b__entry__4 "> <p class="p">内部内存临时表的最大值。</p> <p class="p">如果内存临时表超出了限制，MySQL会自动地把它转化为基于磁盘的MyISAM表。</p> </td> </tr> </tbody></table> </section>